An RYR2-interacting fragment of MYBPC3 mitigates arrhythmia in human iPSC-CM and mouse models of CPVT

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia caused by pathogenic variants in RYR2 that increase its diastolic Ca 2+ release. Current standard of care is insufficient to protect patients from ventricular tachycardia (VT) and sudden death. We identified RYR2 interaction with a subset of MYBPC3 in cardiomyocytes, and validated this interaction by immunostaining, proximity ligation assay, and co-immunoprecipitation. Adeno-associated virus serotype 9 (AAV9)-mediated MYBPC3 overexpression reduced VT in Ryr2 R176Q/+ mice, a model of CPVT. We identified a C-terminal fragment of MYBPC3, C6C10Δ, that is sufficient for RYR2 interaction and anti-arrhythmic activity. Recombinant C6C10Δ reduced the open probability of RYR2-R176Q channels in lipid bilayer single channel recordings, and virally delivered C6C10Δ reduced VT inducibility and duration in the CPVT mouse model and in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) harboring several different CPVT-causing RYR2 variants. In wild-type mice, MyoAAV4E-C6C10Δ did not detectably affect cardiac morphology or systolic function. However, a proportion of MyoAAV4E-C6C10Δ-treated wild-type mice exhibited inducible VT, suggesting proarrhythmic potential that warrants further study. Together, these findings demonstrate that a subset of MYBPC3 interacts with RYR2, and that this interaction may be therapeutically exploited to develop CPVT gene therapy.